Investigation of the Uncertainty of Governing Equation Systems in Thermalhydraulic Calculation

Abstract

Investigation of the effect of uncertainty of the governing equation system on the results of the code ATHLET has been performed on the basis of an uncertainty and sensitivity analysis of the ROSA/LSTF SB-PV-09 experiment. The analysis has been conducted for the 5 and 6 equation systems in ATHLET. The results confirmed that for the selected test case the uncertainties resulting from both momentum equation approximations are very similar. The analysis also showed that some output variables are influenced by approximation of momentum equation, e.g. water level in the core whereas other output variables like maximum clad temperature are not. In some cases the uncertainty of closure relations contributes considerably more to uncertainty of the results than the uncertainty of momentum equation approximation.